History of the UNIX operating system

The first version of UNIX was created in 1969 by Kenneth Thompson and
Dennis Ritchie, system engineers at AT&T's Bell Labs. It went through
many revisions and gained in popularity until 1977, when it was first
made commercially available by Interactive Systems Corporation.

At the same time a team from the University of California at Berkeley
was working to improve UNIX. In 1977 it released the first Berkeley
Software Distribution, which became known as BSD. Over
time this won favour through innovations such as the
C shell.

Meanwhile the AT&T version was developing in different ways. The 1978
release of Version 7 included the Bourne
Shell for the first time. By 1983 commercial interest was growing
and Sun Microsystems produced a UNIX workstation. System
V appeared, directly descended from the original AT&T UNIX and
the prototype of the more widely used variant today.